Heat the oil in a large saucepan over medium-high heat before adding the onion and garlic. Cook until the onion becomes translucent.

Add the ginger, lemongrass and coriander roots and stalks. Cook until the stalks become soft before adding the pumpkin.

Toss the pumpkin in the oil and cook for 5 minutes. Add the water and bring to a boil before reducing the heat to lower. Cook for 30 minutes or until the pumpkin is tender. Remove from heat and allow to cool slightly.

Pour the soup into a blender and blend until smooth. Add most of the chopped coriander (cilantro) leaves reserving some to garnish the soup.

Return to a clean saucepan and add the coconut milk. Serve with shaved coconut, the remaining coriander (cilantro) leaves and chili.